1. Field of the Invention
This invention relates to a banjo type axle casing, and more particularly to improvements in a banjo type axle casing, which is suitable for use in a rear driving axle shaft of a motor car, comprising an enlarged center case portion for housing a differential gear and a pair of sleeve-like case portions outwardly extending from opposite ends of said center case portion for housing an axle shaft.
2. Prior Art
A reduction gear and a differential gear are mounted in the center portion of an axle casing for housing a driving axle shaft in a motor car or the like, and said axle casing is of a banjo type, carrier type or split type in accordance with the form and system thereof. From among those types, a banjo type axle casing 10, as shown in FIG. 1, comprises an enlarged center case portion 10a for housing a differential gear and a pair of sleeve-like case portions 10b outwardly extending from opposite ends of said center case portion 10a for housing an axle shaft. Such a banjo type axle casing includes one in which the center case portion is made of malleable cast iron or cast steel and a steel pipe is pressed into opposite sides of said center case portion, one in which sheets of steel are formed by press work and welded to one another, one entirely made of cast steel, one in which only the center case portion is formed by press work and a steel pipe is welded to opposite sides of said center case portion, or the like. Said banjo type axle casing, in which a reduction gear assembled separately is secured to said axle casing, is convenient for adjusting the reduction gearing and easy to manufacture, and hence, widely used at present. In the axle casings such as said banjo type axle casing, lubricating oil is filled in the inner lower portion of the center case portion for lubricating the differential gear housed in said center case portion. However, heretofore, said lubricating oil has flowed out from the center case portion in a direction of the sleeve-like case portion for housing the axle shaft when the motor car turns in running direction or runs in a laterally tilted condition, and the lubricating oil is temporarily separated from the differential gear, with no lubrication being effected in the differential gear. When this condition is sustained, such disadvantages have been presented that seizure of gears takes place and unusual noises occur.
In order to obviate the disadvantages as described above, a belt-like shield plate made of thin sheet steel or the like and provided at the center thereof with an insert hole for receiving an axle shaft has been fitted in set plates and the like spot-welded to upper and lower portions of the center case portion of the axle casing by utilizing the resiliency of said shield plate so as to have a deflecting action, so that nonuniform distribution of the lubricating oil can be prevented. There have been raised such problems that the fitting property of the shield plate may be low, or a large gap is formed between the axle casing and the shield plate during manufacture, so that the flow of the lubricating oil cannot be always effectively prevented.
On the other hand, to obviate those problems raised with the oil deflector formed only by the conventional belt-like shield plate, such a banjo type axle casing may be proposed which comprises an enlarged center case portion for housing a differential gear and a pair of sleeve-like case portions outwardly extending from opposite sides of said center case portion for housing the axle shaft, and a cylindrical member for covering an axle shaft, the inner end of which is spaced apart at a predetermined interval from the differential gear and the outer end of which is inserted into and engaged with the inner peripheral surface of said sleeve-like case portions. This banjo type axle casing has an advantageous feature of preventing the flow of lubricating oil to a certain extent. However, since the cylindrical member is formed of a thin sheet wound into a cylindrical form and the opposite ends thereof are both restrained, there have been such problems that the cylindrical member is inferior in the fitting property because the inner peripheral surface of the sleeve-like case portions, which is made of two semi-cylindrical members welded to each other, in general, is not a true circle in cross-section and has remaining burrs due to welding, or, when a large slit is formed in the outer end of the cylindrical member so as to improve the fitting property, leakage of lubricating oil through said slit is increased.
In addition, it is conceivable to weld the outer end of the cylindrical member to the inner peripheral surface of the sleeve-like case portions so as to improve the sealing property between the cylindrical member and the inner peripheral surface of the sleeve-like case portions. However, such a welding results in decreased workability, difficulties in removing chips produced by cutting work carried out thereafter, and damages to the differential gear caused by said chips.